Transparent conductive laminate, touch panel and touch panel-equipped liquid crystal display

ABSTRACT

The transparent conductive laminate of the invention is a laminate comprising a film made of a polymer with a photoelastic constant of no greater than 70×10 −12  Pa −1 , a light-scattering layer with a haze value in the range of 0.2-1.4% formed on one side thereof, and a transparent conductive layer formed on the other side thereof, wherein the laminate exhibits an overall retardation of λ/4. By using the laminate it is possible to provide touch panels with reduced light reflection, no coloration, excellent visibility and high reliability for outdoor use, as well as touch panel-equipped liquid crystal displays employing them.

FIELD OF THE INVENTION

The present invention relates to a transparent conductive laminate. Morespecifically, it relates to a transparent conductive laminate that isparticularly suitable for use in touch panels and touch panel-equippedliquid crystal displays.

BACKGROUND ART

Recently, the wide employment of information-processing equipment, onwhich a liquid crystal display for displaying information and a touchpanel (called a touch screen, a transparent membrane switch) forinputting information were mounted, began. Most of the touch panels areresistance film type ones. The resistance film type touch panels arefabricated by setting two transparent electrode substrates (a movableelectrode substrate and a fixed electrode substrate) having transparentconductive layers formed thereon, respectively, facing each other at adistance of 10 to 100 μm. In order to maintain insulation between themovable electrode substrate and fixed electrode substrate in the absenceof external force, dot spacers are usually formed on the electrodesurface of the fixed electrode substrate. Due to this construction atouch by a finger or pen on the outside of the movable electrodesubstrate causes contact between the electrode surfaces of the movableelectrode substrate and fixed electrode substrate only at the touchedsite, thereby resulting in switch and, for example, allowing selectionof a menu on the liquid crystal display or input of a drawn figure orwritten characters.

Such information-processing equipments having touch panel-equippedliquid crystal display are often used in portable form in the case of,for example, camcorders, PDAs (Personal Digital Assistants), smartphones and the like. Because the touch panel-equipped liquid crystaldisplays of such portable information-processing equipments aregenerally used outdoors, they are inevitably used under light sourcesemanating from different directions. Consequently, noise light(reflected light from the touch panel section) also enters the eyesimultaneously with the image recognition light (for example, light fromthe liquid crystal display), thus rendering the display more difficultto distinguish.

Japanese Unexamined Patent Publication HEI No. 5-127822 describes atouch panel which reduces reflected light by a laminated construction ofa ¼ wavelength retardation film, a polarizing plate and anonglare-treated transparent film, in that order on the touch panelsection. The touch panel is effective for reducing reflected light fromthe touch panel section, but coloration of light from the liquid crystaldisplay by the ¼ wavelength retardation film has been a problem.

WO99/66391 discloses a touch panel employing a retardation film having aretardation of 90-200 nm and a photoelastic constant of 5×10⁻¹³ cm²/dyneto 65×10⁻¹³ cm²/dyne (5-65×10⁻¹² Pa⁻¹), and a pair of transparentconductive substrates. This publication also mentions that theretardation film having a transparent conductive layer formed thereoncan be used for the transparent conductive substrate of the touch panel.

However, it has been found that lack of a protective layer on a sideopposite to the transparent conductive layer-formed side of theretardation film can sometimes create problems during actualmanufacturing, such as scratching of the retardation film during theprocess of forming the transparent conductive layer or the processes ofmaking up the touch panel, or can lead to insufficient reliability ofadhesion when the retardation film is attached to the polarizing plate.However, it has become apparent that when a layer, which performs afunction of improving adhesion with the polarizing plate as well as afunction of preventing damage during the various making up processes, isformed on the polarizing plate lamination side of the retardation film,red-green stripes become distinguishable due to film thickness deviationof the layer and thus reduce the visibility of the liquid crystaldisplay.

On the other hand, Japanese Unexamined Patent Publication HEI No.5-50561 discloses a transparent conductive film (transparent conductivelaminate) having one side of the film surface roughened to center lineaverage roughness (Ra) in the range of 0.05-5.0 μm and having atransparent conductive layer formed on the other side, as well as atouch panel having a construction employing the transparent conductivefilm (transparent conductive laminate) as a lower sheet (fixed electrodesubstrate). When a support sheet is set in contact with the lower sheetfor reinforcement of the touch panel, color stripes are produced due tolight interference between the lower sheet and the support sheethitherto, but aforementioned formation of a roughened surface on thelower sheet prevents the light interference-induced color stripes. As amethod of forming the roughened surface there is mentioned a method offorming a layer comprising inorganic fine particles or organic fineparticles. This method is effective for eliminating red-green stripes,but because center line average roughness is too large, the haze isincreased and the visibility of the liquid crystal is thus impaired.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a novel transparentconductive laminate that exhibits a λ/4 retardation.

It is another object of the invention to provide the aforementionedlaminate that has enhanced visibility and is particularly easy to seewhen used in a touch panel.

It is yet another object of the invention to provide a touch panel and atouch panel-equipped liquid crystal display employing the aforementionedlaminate.

These and other objects and advantages of the invention will becomeapparent from the detailed description that follows.

According to the present invention, these objects and advantages areachieved, firstly, by a transparent conductive laminate which comprisesa film made of a polymer with a photoelastic constant of no greater than70×10⁻¹² Pa⁻¹ (polymer film A), a light-scattering layer with a hazevalue in the range of 0.2-1.4% formed on one side thereof, and atransparent conductive layer formed on the other side thereof, andoverall exhibits a λ/4 retardation.

The objects and advantages of the invention are achieved, secondly, by atouch panel and a touch panel-equipped liquid crystal display having theaforementioned laminate situated at a specific position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the touch panel fabricated in Example 1(and Comparative Example 1).

FIG. 2 is a schematic view of the touch panel fabricated in Example 2.

FIG. 3 is a schematic view of the touch panel-equipped liquid crystaldisplay fabricated in Example 3 (and Comparative Example 2).

FIG. 4 is a schematic view of the touch panel-equipped liquid crystaldisplay fabricated in Example 4.

EXPLANATION OF SYMBOLS

-   1: Anti-glare hard coat layer-   2: Light-scattering layer (or transparent resin layer)-   3: Retardation film-   4: Cured resin layer-   5: Transparent conductive layer-   6: Dot spacer-   7: Transparent conductive layer-   8: Glass substrate-   9: High refractive index layer-   10: Low refractive index layer-   11: Retardation film-   12: Polymer film-   13: Polarizing plate-   14-1: Transparent conductive laminate-   14-2: Transparent conductive laminate-   15: Transparent conductive laminate-   16: Transparent conductive laminate-   17: Transparent conductive laminate-   18: Retardation film-   19: Polarizing plate-   20: Retardation film-   21: Liquid crystal cell-   22: Polarizing plate

PREFERRED EMBODIMENTS OF THE INVENTION

The transparent conductive laminate of the invention comprises a filmmade of a polymer (hereinafter referred to as “polymer film A”), alight-scattering layer on one side thereof and a transparent conductivelayer on the other side thereof. Also, the laminate overall exhibits aλ/4 retardation.

Polymer film A may consist of a single layer film, or it may be composedof a laminate of two or more films.

When it consists of a single layer film, it may be a film having afunction exhibiting a λ/4 retardation by the single layer film alone, orin other words, it may be a λ/4 retardation film.

When the polymer film A is composed of a laminate of two or more films,it may be, for example, (i) a laminated film having a single layer filmexhibiting λ/4 retardation set in contact with a single layer filmhaving excellent optical isotropy (for example, a retardation (Δnd)value of no greater than 30 nm), (ii) a laminated film having a singlelayer film exhibiting a λ/4 retardation and a single layer filmexhibiting a λ/2 retardation set in contact with a single layer filmhaving excellent optical isotropy (for example, a retardation (Δnd)value of no greater than 30 nm), or (iii) a laminated retardation filmcomprising a single layer film exhibiting λ/4 retardation and a filmexhibiting a λ/2 retardation.

The method for obtaining the film exhibiting a λ/4 retardation or a λ/2retardation may be, for example, a method wherein a film made of apolymer with a photoelastic constant of no greater than 70×10⁻¹² Pa⁻¹ isuniaxially stretched (or biaxially stretched either successively orsimultaneously) to exhibit a λ/4 retardation or a λ/2 retardation in thepolymer film itself, or a method wherein a layer of a compoundexhibiting a λ/4 retardation or a λ/2 retardation (for example, a layercomposed of polymer liquid crystals) is formed on a polymer film with aphotoelastic constant of no greater than 70×10⁻¹² Pa⁻¹.

By using the polymer film A it is possible to provide a transparentconductive laminate exhibiting overall λ/4 retardation. In particular,the polymer film A is preferably a laminated film having a single layerfilm exhibiting a λ/4 retardation and a single layer film exhibiting aλ/2 retardation laminated in contact with a single layer film havingexcellent optical isotropy (for example, a retardation (Δnd) value of nogreater than 30 nm), or a laminated retardation film comprising a singlelayer λ/4 retardation film and a single layer λ/2 retardation film, inorder to exhibit overall an excellent wide-range λ/4 retardation.

A preferred embodiment of the invention is shown in FIG. 1. FIG. 1 is aschematic view of the touch panel fabricated in Example 1 describedbelow. The transparent conductive laminate P (14-1) shown in FIG. 1 hasa construction wherein a transparent conductive layer (5) is situated onone side of a polymer film A (3: λ/4 retardation film) via a cured resinlayer (4), and a light-scattering layer (2) is formed on the other sideof the polymer film A. The polymer film A has the function of producingoverall a λ/4 retardation for the transparent conductive laminate P(14-1). The transparent conductive laminate P (14-1) is also laminatedwith a polarizing plate (13), and a transparent conductive laminate R(15) is situated under these across a gap to construct a touch panel.

The transparent conductive laminate of the invention also includes typeswherein another film made of a polymer with a photoelastic constant ofno greater than 70×10⁻¹² Pa⁻¹ (hereinafter referred to as polymer filmB) is laminated on the surface of the aforementioned polymer film Aopposite to the side on which the transparent conductive layer isformed.

In this case, the function of either the polymer film A or polymer filmB may provide the laminate with overall a λ/4 retardation, or thecombined function of the polymer film A and polymer film B may providethe laminate with overall a λ/4 retardation. The in-plane retardationvalue required for polymer film A will differ depending on itsrelationship with polymer film B.

For a laminate wherein the function of the polymer film A provides thelaminate with overall a λ/4 retardation, the embodiment described abovemay be used as the polymer film A. In such cases, the polymer film B maybe one with excellent optical isotropy (for example, a retardation value(Δnd) of no greater than 30 nm), which does not inhibit the overalleffect. Such a polymer film B is preferably used together with thepolymer film A as the electrode substrate for the touch panel, so as tobecome a support for increased overall strength.

As laminate wherein the function of the polymer film B provides a λ/4retardation for the laminate overall, there may be mentioned exampleswherein the polymer film A is a film with excellent optical isotropy(for example, a retardation value (Δnd) of no greater than 30 nm), andthe polymer film B is (i) a single layer film exhibiting a λ/4retardation or (ii) a laminated retardation film having a single layerfilm exhibiting a λ/4 retardation and a single layer film exhibiting λ/2retardation.

The method for obtaining a film exhibiting a λ/4 retardation or a λ/2retardation may be, for example, a method wherein a film made of apolymer with a photoelastic constant of no greater than 70×10⁻¹² Pa⁻¹ isuniaxially stretched (or biaxially stretched either successively orsimultaneously) to exhibit a λ/4 retardation or a λ/2 retardation in thepolymer film itself, or a method wherein a layer of a compoundexhibiting a λ/4 retardation or a λ/2 retardation (for example, a layercomposed of polymer liquid crystals) is formed on a polymer film with aphotoelastic constant of no greater than 70×10⁻¹² Pa⁻¹. In a laminatewherein the polymer film B functions to provide a laminate exhibitingoverall a λ/4 retardation, the polymer film B is most preferably alaminated retardation film having a single layer λ/4 retardation filmand a single layer λ/2 retardation film, in order to exhibit overall anexcellent wide-range λ/4 retardation.

In a laminate wherein the polymer film A and polymer film B bothfunction to provide a laminate exhibiting overall a λ/4 retardation, theaforementioned film exhibiting a λ/4 retardation may be used for eitherthe polymer film A or polymer film B, while using the aforementionedfilm exhibiting a λ/2 retardation as the other.

In particular, using a single λ/4 retardation film as the polymer film Aand a single λ/2 retardation film as the polymer film B is preferred inorder to exhibit overall an excellent wide-range λ/4 retardation by theaction of both the polymer films A and B.

A preferred embodiment of the invention is shown in FIG. 4. FIG. 4 is aschematic view of the touch panel-equipped liquid crystal display ofExample 4 described below. In FIG. 4, a transparent conductive layer (5)is situated on one side of a polymer film A (12: optical isotropy film)via a cured resin layer (4), a high refractive index layer (9) and lowrefractive index layer (10) while a light-scattering layer (2) is formedon the other side of the polymer film A, and polymer film B (a laminatedretardation film comprising a λ/4 retardation film (11) and a λ/2retardation film (3)) is set thereover. In this case, the polymer film B(the laminated retardation film) exhibits overall a λ/4 retardation forthe transparent conductive laminate P (17). A touch panel may beconstructed with a laminate comprising a polarizing plate (13) and theaforementioned transparent conductive laminate P (17), and a transparentconductive laminate R (16) situated under these across a gap. This touchpanel may then be laminated with a liquid crystal cell (21) and apolarizing plate (22) to construct a touch panel-equipped liquid crystaldisplay.

The liquid crystal cell comprises liquid crystals enclosed betweentransparent conductive substrates, but display cannot be achieved with aliquid crystal cell alone. A liquid crystal display functions bycombination of a liquid crystal cell, a polarizing plate and aretardation film.

<Polymer Film A>

The polymer film A used for the invention has a photoelastic constant ofno greater than 70×10⁻¹² Pa⁻¹, and preferably no greater than 64×10⁻¹²Pa⁻¹. In a touch panel constructed using a transparent conductivelaminate having a transparent conductive layer formed on a conventionalfilm made of a polymer having a photoelastic constant exceeding 70×10⁻¹²Pa⁻¹, together with a polarizing plate and a retardation film,coloration often occurs in an arc shape from the bonded section (seal)toward the inside upon heating at 80° C. In a touch panel employing apolymer film A according to the invention, such coloration can benotably inhibited. By also using a film A made of a polymer having aphotoelastic constant of no greater than 70×10⁻¹² Pa⁻¹, it is alsopossible to notably inhibit variation in the retardation during themanufacturing processes. There are no particular restrictions on thelower limit of the photoelastic constant, but it will normally be0.5×10⁻¹² Pa⁻¹ (0.5×10⁻¹³ cm²/dyne).

As polymers having photoelastic constants of no greater than 70×10⁻¹²Pa⁻¹ there may be mentioned thermoplastic resins such as fluorene ring-or isophorone ring-containing aromatic polycarbonates. Specifically,they are polycarbonates in which a repeating unit represented by thefollowing formula (I) accounts for 70-30 mole percent and preferably70-35 mole percent of the total repeating units.

In formula (I), R₁-R₈ each independently represent at least one groupselected from among hydrogen, halogens and C1-6 hydrocarbon groups. Asexamples of hydrocarbon groups there may be mentioned alkyl groups suchas methyl and ethyl, or aryl groups such as phenyl.

X may be a group represented by the following formula:

(fluorene component), or a group represented by the following formula:

(isophorone component). R₉ and R₁₀ each independently representhydrogen, a halogen or a C1-3 alkyl group such as methyl.

More preferred polycarbonate materials are those composed of a repeatingunit represented by formula (I) above and a repeating unit representedby the following formula (II):

wherein the repeating unit represented by formula (I) accounts for 70-30mole percent of the total repeating units of the polycarbonate, based onthe total of formulas (I) and (II) above.

R₁₁-R₁₈ in formula (II) above each independently represent at least onegroup selected from among hydrogen, halogens and C1-22 hydrocarbongroups, and Y represents at least one group selected from among groupsrepresented by the following formulas.

Among the groups for Y, R₁₉-R₂₁, R₂₃ and R₂₄ each independentlyrepresent hydrogen, a halogen or a C1-22 hydrocarbon group such as analkyl and aryl group, R₂₂ and R₂₅ each independently represent a C1-22hydrocarbon group such as an alkyl or aryl group, and Ar₁-Ar₃ eachindependently represent a C6-10 aryl group such as phenyl.

More preferably, the polycarbonate is a polycarbonate comprising arepeating unit represented by the following formula (III):

and a repeating unit represented by the following formula (IV).

In formula (III) above, R₂₆ and R₂₇ each independently representhydrogen or methyl. R₂₆ and R₂₇ are both preferably methyl.

In formula (IV) above, R₂₈ and R₂₉ each independently represent hydrogenor methyl, and preferably hydrogen.

The polycarbonate may be a copolymer, or a polymer blend (blend or blendpolymer). Two or more different types of copolymers may also becombined, or two or more different homopolymers or a homopolymer and acopolymer may be blended.

As examples of polymers having photoelastic constants of no greater than70×10⁻¹² Pa⁻¹ (70×10⁻¹³ cm²/dyne) there may be mentioned, in addition tothose referred to above, cycloolefin polymer. As polymer films made ofcycloolefin polymer there may be mentioned “TPX” and “APO” by MitsuiPetroleum Chemicals Co., Ltd., and “ZEONOR” by Nihon Zeon, and “ARTON”by JSR Co., Ltd.

The polymer used to manufacture the polymer film A is preferably onewith high heat resistance because of the ordinary heating processes formanufacturing the transparent conductive laminate or making thetransparent conductive laminate into a touch panel.

Heat resistance is correlated with the glass transition temperature(Tg), and DSC may measure the Tg. In the case of using a polymer with alow photoelastic constant, if the Tg of the polymer is 10° C. or morehigher than the process temperature, the retardation of the film in theprocess will be prevented from varying. In the case of a polymer with arelatively high photoelastic constant, the Tg is preferably at least 45°C. above the process temperature in order to prevent retardationvariation in the process. For example, if the process temperature is125° C., and a cycloolefin polymer having a photoelastic constant of nogreater than 7×10⁻¹² Pa⁻¹ (7×10⁻¹³ cm²/dyne) is used, the Tg ispreferably at least 135° C. In the case of a thermoplastic resin such asa polycarbonate resin having a photoelastic constant of 39-70×10⁻¹² Pa⁻¹(70×10⁻¹³ cm²/dyne), the Tg is preferably at least 170° C.

The method for manufacturing the polymer film A may be a publicly-knownmelt extrusion method, solution casting method or the like. The solventfor solution casting is preferably methylene chloride, dioxolane or thelike in the case of the aforementioned polycarbonate, for example.

The thickness of the polymer film A will usually be 50-200 μm, andpreferably 70-150 μm.

The transparent conductive laminate of the invention is characterized byexhibiting a λ/4 retardation as the laminate itself. That is, thelaminate of the invention has the same function as a “λ/4 retardationfilm”, whereby linear polarized light, which has passed through apolarizing plate, and then passes from one side of the laminate of theinvention through to the other side, can be converted to circularpolarized light.

Thus, when fabricating a touch panel using a laminate comprising apolarizing plate and a transparent conductive laminate of the invention,together with another transparent conductive laminate situated underthem across a gap, it is possible to reduce reflection of external lighton the touch panel.

The principle by which reflection of external light on the touch panelis reduced is as follows.

Specifically, incident light which has passed through a polarizing plateon the input operation side, that is to say linear polarized lightpasses through the ¼ wavelength retardation film on the movableelectrode substrate side and is converted to circular polarized light,which is reflected at the electrode surface of a movable electrodesubstrate or the electrode surface of a fixed electrode substrate, tobecome reverse circular polarized light. When it again passes throughthe ¼ wavelength retardation film on the movable electrode substrateside, it is converted to linear polarized light. The plane ofpolarization is rotated 90°against the incident light and is thereforeabsorbed by the polarizing plate, thus inhibiting reflection of thetouch panel.

Touch panel-equipped liquid crystal displays employing a transparentconductive laminate of the invention may be classified into thefollowing two types, which will be referred to as “circular polarizingplate type” and “integrated type” for the purpose of the invention.

(1) Circular Polarizing Plate Type

A circular polarizing plate type touch panel-equipped liquid crystaldisplay of the invention has a construction with a touch panelcomprising a laminate of a polarizing plate 1 and a transparentconductive laminated body P exhibiting a λ/4 retardation, together withanother transparent conductive laminate R situated under them across agap, a retardation film 2, a polarizing plate 2, a retardation film 3, aliquid crystal cell and a polarizing plate 3, laminated in that orderfrom the input operation side.

Here, the liquid crystal display is constructed with the polarizingplate 2, retardation film 3, liquid crystal cell and polarizing plate 3.The transparent conductive laminate R must have a retardation value ofno greater than 30 nm so that it may not affect the polarized light. Theretardation film 2 is a λ/4 retardation film, and the optical axis ofthe transparent conductive laminate P and the optical axis of theretardation film 2 are mutually orthogonal. When light exiting from thepolarizing plate 2 passes through the two ¼ wavelength retardation filmswhose optical axes are mutually orthogonal, the retardation isessentially cancelled out, so that the polarized light reaches thepolarizing plate on the input operation side without undergoing anyalteration whatsoever and either passes through the polarizing plate oris absorbed by the polarizing plate to produce an image. It is therebypossible to prevent coloration of light leaving the polarizing plate 2.

(2) Integrated Type

An integrated type touch panel-equipped liquid crystal display of theinvention has a construction with a touch panel comprising a laminate ofa polarizing plate 1 and a transparent conductive laminated body Pexhibiting a λ/4 retardation, together with another transparentconductive laminate R situated under them across a gap, a liquid crystalcell and a polarizing plate 3, laminated in that order from the inputoperation side.

Here, the liquid crystal display is constructed with the polarizingplate 1, a transparent conductive laminated body P exhibiting a λ/4retardation, a liquid crystal cell and a polarizing plate 3. Since thereis no effect on polarized light if the retardation value of thetransparent conductive laminate R is 30 nm or less, almost no colorationoccurs even when it is integrated into a touch panel.

To exhibit a λ/4 retardation is, ideally, to exhibit a λ/4 retardationwith respect to all of the wavelengths in the visible light range.However, when retardation at a wavelength of 550 nm is λ/4, there is noproblem in practice even if the retardation deviates somewhat from λ/4at other wavelengths. The retardation value (Δnd) at a wavelength of 550nm is preferably 125-150 nm, and more preferably 131-145 nm. Aretardation value above or below this range is not preferred because itwill decrease the reflection-reducing effect for external light whenused in combination with the polarizing plate.

In the circular polarizing plate type described above, the retardationfilm 2 is preferably a λ/4 retardation film to increase visibility.

There are no particular restrictions on the material used to manufacturethe retardation film 2, but the difference in the retardation value withrespect to the transparent conductive laminate P of the invention at awavelength of 550 nm is preferably no greater than 10 nm. Coloration maybecome noticeable if the retardation value difference is greater than 10nm. Coloration may also become noticeable with a large difference inwavelength dispersion between the transparent conductive laminate P andthe retardation film 2. Consequently, the difference in wavelengthdispersion between the transparent conductive laminate P and theretardation film 2 is preferably small. Specifically, representing theretardation values at wavelengths of 450 nm, 550 nm and 650 nm asR(450), R(550) and R(650) respectively, when the wavelength dispersionof the transparent conductive laminate P is R(450)/R(550)>1 andR(650)/R(550)<1, the wavelength dispersion of the retardation film 2 isalso preferably R(450)/R(550)>1 and R(650)/R(550)<1. Conversely, whenthe wavelength dispersion of the transparent conductive laminate P isR(450)/R(550)<1 and R(650)/R(550)>1, the wavelength dispersion of theretardation film 2 is also preferably R(450)/R(550)<1 andR(650)/R(550)>1.

Forming a transparent conductive layer on at least one side of theretardation film 2 can confer an electromagnetic wave shield function.

In order to control wavelength dispersion of retardation, for example, acompound layer (for example, a polymer liquid crystal layer) exhibitingretardation may be formed on the polymer films A, B, or a compound suchas low molecular liquid crystals may be included in the polymer films A,B, in a range which does not impede the effect of the invention.

The polymer film B may be made of the same material as the polymer filmA. The film thickness and manufacturing process may also be the same asfor the polymer film A.

<Light-Scattering Layer>

A light-scattering layer is formed on one side of the polymer film A.The light-scattering layer has the function of scattering light, but itmay also sometimes function to enhance the cohesion between the polymerfilm A and the polymer film B or the polymer film A and the polarizingplate, or to act as a layer with the function of preventing scratches ofthe polymer film A during manufacturing process of the transparentconductive laminate. The light-scattering layer alone has a haze valueof 0.2-1.4%, and preferably 0.3-1%. The haze value of thelight-scattering layer alone may be determined as the difference in thehaze value before formation and after formation of the light-scatteringlayer on the polymer film A. If the haze value of the light-scatteringlayer alone is less than 0.2%, red-green stripes become distinguishabledue to film thickness deviation, thus reducing the visibility of theliquid crystal display. The slip property is also impaired, therebyeliminating the effect of preventing scratches of the polymer film Aduring manufacturing process of the transparent conductive laminated. Ahaze value of greater than 1.4% will also tend to impair the visibilityof the liquid crystal display.

The thickness of the light-scattering layer is preferably 1-5 μm andmore preferably 1-4 μm. When the surface contains unevenness and is notsubstantially flat, the thickness is defined as the average value ofmeasuring the film thickness at more than 10 arbitrary points.

The light-scattering layer scatters light inside and/or on the surfaceof the layer. The method of forming the light-scattering layer on thesurface of the polymer film A may be, for example, a method of forming apolymer layer containing fine particles, or a method of producingfine-unevenness on the surface during forming a polymer layer containingno fine particles. In the former method, light scattering occurs insidethe light-scattering layer due to the use of fine particles that have adifferent refractive index than the polymer. By using particles having alarger mean diameter than the thickness of the polymer layer, lightscattering will occur on the surface regardless of the refractive indexof the fine particles, because fine unevenness will be produced on thesurface. In the latter method, unevenness may be formed by contacting anemboss roll or the like with the surface of the polymer layer duringforming the polymer layer.

The light-scattering layer will have unevenness except in the case ofutilizing only light scattering inside the light-scattering layer, andas surface texture parameter, a center line average roughness (Ra) ispreferably in the range of 0.005-0.04 μm.

A polymer layer containing fine particles may be formed on the surfaceof the polymer film A by, for example, coating, spraying or lamination.

As examples of fine particles to be used to form a polymer layercontaining fine particles by coating, there may be mentioned silica fineparticles, crosslinked acrylic fine particles, crosslinked polystyrenefine particles and the like. The haze value of the light-scatteringlayer may be adjusted by varying a diameter of the fine particles, themixing ratio of the fine particles to polymer, and the film thickness ofthe polymer layer.

Examples of polymers include silicon atom-containing polymers obtainedusing silicon alkoxides such as methyltriethoxysilane orphenyltriethoxysilane as monomers, melamine thermosetting resins such asetherified methylolmelamine or the like, phenoxy thermosetting resins,epoxy thermosetting resins, and polyfunctional acrylate resins obtainedusing polyfunctional acrylate monomers such as polyol acrylates,polyester acrylates, urethane acrylates, epoxy acrylates or the like.These acrylate resins may be either thermosetting resins or radiationcuring resins. Radiation curing resins are resins that undergopolymerization by irradiation with ultraviolet rays, electron beams orthe like.

Among these, polyfunctional acrylate monomers which undergopolymerization by irradiation facilitate the production process becausethey yield polymer layers with a high degree of crosslinking within arelatively short period of time. They are also preferred because of thehigh strength of the resulting layers themselves.

As polyfunctional acrylate monomers there may be mentioned thosecontaining polyfunctional acrylate components having two or moreacryloyl groups in the unit structure. Specific examples thereof whichare preferred for such uses include various acrylate monomers such astrimethylolpropane triacrylate, trimethylolpropane ethyleneoxide-modified triacrylate, trimethylolpropane propylene oxide-modifiedtriacrylate, isocyanuric acid ethylene oxide-modified triacrylate,pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate,dipentaerythritol hexaacrylate and dimethyloltricyclodecane diacrylate,as well as polyfunctional acrylate oligomers such as polyester-modifiedacrylates, urethane-modified acrylates, epoxy-modified acrylates and thelike. These resins may be used as simple composition or as mixedcomposition of a plurality of types, and depending on the case, anappropriate amount of a silicon alkoxide hydrolysis condensate ispreferably added to the composition.

When polymerization of the resin layer is carried out with ultravioletirradiation, an appropriate amount of a publicly-known photoinitiator isadded. As examples of photoinitiators there may be mentionedacetophenone-based compounds such as diethoxyacetophenone,2-methyl-1-{4-(methylthio)phenyl}-2-morpholinopropane,2-hydroxy-2-methyl-1-phenylpropan-1-one and 1-hydroxycyclohexylphenylketone; benzoin-based compounds such as benzoin and benzyldimethylketal; benzophenone-based compounds such as benzophenone andbenzoylbenzoic acid; and thioxanthone-based compounds such asthioxanthone and 2,4-dichlorothioxanthone.

As phenoxy thermosetting resin layers there may be mentioned polymerlayers obtained by thermally crosslinking phenoxy resins, phenoxyetherresins and phenoxyester resins represented by formula (1) below withpolyfunctional isocyanate compounds.

In formula (1), R¹-R⁶ may be the same or different and representhydrogen or C1-3 alkyl, R⁷ represents C2-5 alkylene, X represents anether or ester, m represents an integer of 0-3 and n represents aninteger of 20-300. Most preferably, R¹ and R² are methyl, R³-R⁶ arehydrogen and R⁷ is pentylene from the standpoint of facilitatingsynthesis and increasing productivity.

The polyfunctional isocyanate compound may be any compound having two ormore isocyanate groups in the molecule, and examples thereof includepolyisocyanates such as 2,6-tolylene diisocyanate, 2,4-tolylenediisocyanate, tolylene diisocyanate-trimethylolpropane adduct,t-cyclohexane-1,4-diisocyanate, m-phenylene diisocyanate, p-phenylenediisocyanate, hexamethylene diisocyanate, 1,3,6-hexamethylenetriisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate,tlidine diisocyanate, xylylene diisocyanate, hydrogenated xylylenediisocyanate, diphenylmethane-4,4′-diisocyanate, hydrogenateddiphenylmethane-4,4′-diisocyanate, lysine diisocyanate, lysine estertriisocyanate, triphenylmethane triisocyanate, tris(isocyanatophenyl)thiophosphate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylenediisocyanate, 1,6,11-undecane triisocyanate,1,8-diisocyanate-4-isocyanate methyloctane, bicycloheptanetriisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and2,4,4-trimethylhexamethylene dilsocyanate, as well as their mixtures orpolyhydric alcohol addition products. From the standpoint of generalpurpose use and reactivity, 2,6-tolylene diisocyanate, 2,4-tolylenediisocyanate, tolylene diisocyanate-trimethylolpropane adduct andhexamethylene diisocyanate are preferred.

In addition, a publicly-known tertiary amine such as triethylenediamineor an organic tin compound such as dibutyltin dilaurate may be added inan appropriate amount as a reaction accelerator to improve thecrosslinking speed.

Various resins may be used as the epoxy thermosetting resin layer, butlayers obtained by thermally crosslinking novolac epoxy resinsrepresented by formula (2) below are preferred.

In formula (2) above, R⁸ represents hydrogen or methyl, and R⁹represents hydrogen or glycidyl phenyl ether. The letter q represents aninteger of 1-50, and although the value of q is in reality difficult tospecify because it generally has a distribution, it preferably has alarge average that is preferably at least 3 and more preferably at least5.

A publicly-known curing agent may be employed for crosslinking of theepoxy resin. For example, there may be used curing agents such asamine-based polyaminoamides, acids and acid anhydrides, imidazoles,mercaptanes, phenol resins and the like. Acid anhydrides and alicyclicamines are preferred among these, with acid anhydrides being morepreferred. As acid anhydrides there may be mentioned alicyclic acidanhydrides such as methylhexahydrophthalic anhydride andmethyltetrahydrophthalic anhydride, aromatic acid anhydrides such asphthalic anhydride and aliphatic acid anhydrides such asdodecenylphthalic anhydride, with methylhexahydrophthalic anhydridebeing particularly preferred. As alicyclic amines there may be mentionedbis(4-amino-3-methyldicyclohexyl)methane, diaminocyclohexylmethane,isophoronediamine and the like, withbis(4-amino-3-methyldicyclohexyl)methane being particularly preferred.

When an acid anhydride is used as the curing agent, a reactionaccelerator may be added to accelerate the curing reaction between theepoxy resin and the acid anhydride. As reaction accelerators there maybe mentioned publicly-known secondary and tertiary amines such asbenzylmethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, pyridine and1,8-diazabicyclo(5,4,0)undecene-1 or curing catalysts such asimidazoles.

As silicon alkoxide polymer layers there are preferably used mixtures oftwo or more different bi- to tetra-functional, and preferably tri- ortetra-functional silicon alkoxides, which are preferably first subjectedto suitable hydrolysis and dehydrating condensation in solution forsufficient oligomerization.

Examples of silicon alkoxides include tetramethoxysilane,tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane,dimethyldimethoxysilane, γ-glycidoxypropyl trimethoxysilane,β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, vinyltrimethoxysilane,N-β(aminoethyl)-γ-aminopropyltrimethoxysilane,N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane andγ-aminopropyltriethoxysilane.

Polymerization of these silicon alkoxides is accelerated by heating, butif necessary the coated film layer may be irradiated with active lightrays such as ultraviolet rays to further increase the degree ofcrosslinking.

<Transparent Conductive Layer>

A transparent conductive layer is formed on the side of the polymer filmA opposite to the side on which the aforementioned light-scatteringlayer is formed.

The transparent conductive layer used for the invention is a layercomposed of a metal oxide. As examples of metal oxides there may bementioned indium oxides containing tin, tellurium, cadmium, molybdenum,tungsten, fluorine and zinc, antimony-containing tin oxides, and oxidescomposed of tin oxide and cadmium oxide. Indium oxides containing tin(ITO) are preferred among these from the viewpoint of transparency andconductivity. Silicon, titanium, zinc or the like is preferably added asa third component to ITO.

The thickness of the transparent conductive layer is preferably at least15 nm in order to achieve sufficient conductivity, and it is preferablyno greater than 150 nm in order to obtain a film with sufficiently hightransparency. The thickness is most preferably 17-140 nm.

<Cured Resin Layer>

Before forming the transparent conductive layer on the side of thepolymer film A opposite to the side on which the light-scattering layeris formed, a cured resin layer is preferably formed on the surface ofthe polymer film A. The presence of a cured resin layer will preventdamage to the polymer film A by solvents during the process ofmanufacturing the touch panel. The thickness of the cured resin layer ispreferably 0.1-10 μm, and more preferably 2-10 μm. The cured resin layerdoes not have to be a single layer, and may instead be a laminate of twoor more layers. An anchor layer may be formed between the cured resinlayer and the polymer film A for improved cohesion between them.

The cured resin used to form the cured resin layer may be the samepolymer used to form the light-scattering layer.

Formation of unevenness on the cured resin layer surface by adding fineparticles into the cured resin layer can prevent Newton rings generatedbetween the movable electrode substrate and the fixed electrodesubstrate, for an effect of enhanced visibility. As examples of fineparticles to be added to the cured resin layer there may be mentionedsilica fine particles, crosslinked acrylic fine particles andcrosslinked polystyrene fine particles. The unevenness on the surfacemay be controlled by varying the diameter of the fine particles, themixing ratio of the fine particles to cured resin, and the filmthickness of the cured resin layer.

If the cured resin layer containing fine particles as described abovesatisfies the following conditions:

-   -   (A) comprising (i) a cured resin component, (ii) at least one        type of fine particle A having a mean primary diameter of 0.5-5        μm and (iii) at least one type of superfine particle B selected        from the group consisting of metal oxides and/or metal fluorides        having a mean primary diameter of no greater than 100 nm,    -   (B) having a fine particle A content of at least 0.3 part by        weight and less than 1.0 part by weight to 100 parts by weight        of the resin component,    -   (C) having a fine particle B content of at least 1 part by        weight and no greater than 20 parts by weight to 100 parts by        weight of the resin component, and    -   (D) having a film thickness of 0.5-5 μm, its function will        prevent Newton rings generated between the movable electrode        substrate and the fixed electrode substrate, and this is        preferred to reduce sparkling of the liquid crystal display.

The type of compound of the fine particles A is not particularlyrestricted so long as the mean primary diameter is 0.5-5 μm. Forexample, there may be employed fine particles of SiO₂, or fine particlescomposed of SiO₂ as the main component or crosslinking component, orfine particles composed mainly of a styrene-based, acrylic-based orbutadiene-based polymer. Such fine particles may also be treated forsurface modification or the like. Two or more different types of fineparticles may also be used in combination. The fine particles A may alsoconsist of a mixture of materials with different mean primary diameterin order to obtain the diameter distribution. According to the inventionthere are no particular restrictions on the content of the fineparticles A, but the fine particle A content is preferably at least 0.3part by weight and less than 1.0 part by weight, more preferably 0.3-0.9part by weight, and even more preferably 0.3-0.8 part by weight, withrespect to 100 parts by weight of the cured resin component. If thecontent is less than 0.3 part by weight it will be difficult to inhibitgeneration of Newton rings. The content is preferably not greater than1.0 part by weight because, although generation of Newton rings can besatisfactorily prevented, the haze value increases and tends to causefuzziness of image and character data on the liquid crystal display.

Any fine particles B having a mean primary diameter of no greater than100 nm may be used, with no particular restrictions on the type ofcompound. As examples there may be mentioned fine particles composed ofmetal oxides such as Al₂O₃, Bi₂O₃, CeO₂, In₂O₃, (In₂O₃.SnO₂), HfO₂,La₂O₃, MgF₂, Sb₂O₅, (Sb₂O₅SnO₂), SiO₂, SnO₂, TiO₂, Y₂O₃, ZnO and ZrO₂,or metal fluorides. Two or more types of compound may also be used incombination. A metal oxide and metal fluoride may also be usedsimultaneously. However, if the superfine particles B have a refractiveindex that is larger than the refractive index of the cured resincomponent, the haze value of the obtained cured resin layer will be toohigh. Consequently, the superfine particles B preferably have a lowerrefractive index in order to increase the options for the cured resincomponent. As examples of such materials there may be mentioned SiO₂,MgF₂ and the like. Since the superfine particles B have a very largesurface to volume ratio and therefore generally tend to aggregate, theywill usually be produced and sold in the form of a slurry, dispersed ina solvent with addition of a dispersing agent. Examples of dispersingagents to be used include aliphatic amine-based, sulfonic acidamide-based, e-caprolactone-based, hydrostearic acid-based,polycarboxylic acid-based and polyester amine-based types. Thedispersion medium (solvent) used may be an ordinary one such as alcohol,water, a ketone or an aromatic-based solvent.

A smaller mean primary diameter of the superfine particles B ispreferred in order to avoid whitening of the cured resin layer byinternal haze, and it is preferably no greater than 100 nm. The meanprimary diameter of the superfine particles B is more preferably nogreater than 80 nm, and even more preferably no greater than 60 nm. Thelower limit is not particularly restricted but is preferably 5 nm. Themean primary diameter of the superfine particles B may be measured usinga laser scattering particle size distribution analyzer. The actual sizescan also be easily measured using a transmission electron microscope orthe like. Specifically, the cured resin layer containing the superfineparticles B is embedded in an epoxy resin or the like and the epoxyresin layer is thoroughly cured and then thinly sliced with a microtometo prepare a measuring sample. The measuring sample is then observedwith a transmission electron microscope, the sizes of the superfineparticles are randomly measured at 10 locations and the measured valuesare averaged to determine the mean primary diameter.

The content of the superfine particles B dispersed in the cured resinlayer may be 1-20 parts by weight, preferably 2-10 parts by weight andmore preferably 3-7 parts by weight of superfine particles B withrespect to 100 parts by weight of the cured resin component. Thesuperfine particles B have an effect of leveling the cured resin layer.A superfine particle B content in the aforementioned range will resultin formation of suitable unevenness on the cured resin layer surface bya synergistic effect with the fine particles A, and unevenness on thesurface will thus provide a function of preventing generation of Newtonrings while also reducing sparkling on the liquid crystal display. Ifthe superfine particle B component is present at less than 1 part byweight, leveling of the cured resin layer will be more difficult andunevenness on the cured resin layer surface will be too large, such thatsparkling will become more noticeable on the liquid crystal display. Ifthe superfine particle B component is present at greater than 20 partsby weight, leveling of the cured resin layer will become too pronounced,thereby an adequate function of preventing Newton rings won't be putforth.

<Optical Interference Layer>

An optical interference layer may be formed between the polymer film Aand the transparent conductive layer. The color tone of the touch panelcan improve by forming an optical interference layer.

The position of the optical interference layer is between the polymerfilm A and the transparent conductive layer, and from the standpoint ofproductivity and effect, it is convenient to form the cured resin layer,optical interference layer and transparent conductive layer in thatorder from the polymer film A side.

The optical interference layer is composed of a high refractive indexlayer and a low refractive index layer, with the low refractive indexlayer preferably in contact with the transparent conductive layer. Thehigh refractive index layer and low refractive index layer are made ofcrosslinked polymers, and either or both the high refractive index layerand low refractive index layer preferably contain superfine particleswith a mean primary diameter of no greater than 100 nm. The crosslinkedpolymer used may be a crosslinked polymer obtained from hydrolysis andcondensation polymerization of a metal alkoxide, or alternatively acrosslinked polymer of a thermosetting resin or radiation curing resin.

Among crosslinked polymers obtained from hydrolysis and condensationpolymerization of metal alkoxides, there are preferred crosslinkedpolymers obtained from hydrolysis and condensation polymerization oftitanium alkoxides and zirconium alkoxides, as well as alkoxysilanes,from the standpoint of achieving excellent mechanical strength,stability and cohesion.

Examples of titanium alkoxides include titanium tetraisopropoxide,tetra-n-propyl orthotitanate, titanium tetra-n-butoxide andtetrakis(2-ethylhexyloxy) titanate, and examples of zirconium alkoxidesinclude zirconium tetraisopropoxide and zirconium tetra-n-butoxide.

Examples of alkoxysilanes include tetramethoxysilane, tetraethoxysilane,methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane,γ-glycidoxypropyl trimethoxysilane,β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, vinyltrimethoxysilane,N-β(aminoethyl)-γ-aminopropyltrimethoxysilane,N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane andγ-aminopropyltriethoxysilane. These alkoxysilanes are preferably used inmixtures of two or more in most cases, as necessary, from the standpointof mechanical strength and cohesion of the layer and solvent resistance,and an amino group-containing alkoxysilane is preferably present in arange of 0.5-60% based on the total weight of the alkoxysilanecomposition.

These metal alkoxides may be used as monomers or as suitable oligomersobtained by hydrolysis and dehydrating condensation, but normally theywill be dissolved in an appropriate organic solvent to prepare a dilutedcoating solution for coating onto a substrate. The coated film layerformed on the substrate undergoes hydrolysis due to moisture in the air,followed by dehydrating condensation. Condensation polymerization canusually only proceed with appropriate heat treatment, and heat treatmentfor a few minutes or longer at a temperature of 100° C. or above duringthe coating process is preferred. In some cases, the heat treatment maybe carried out in tandem with irradiation of the coated layer withactive light rays such as ultraviolet rays, to further increase thedegree of crosslinking.

As diluting solvents there may be used alcohol-based andhydrocarbon-based solvents, of which preferred examples include ethanol,2-propanol, butanol, 2-methyl-1-propanol, 1-methoxy-2-propanol, hexane,cyclohexane and ligroin, but there may also be used polar solvents suchas xylene, toluene, cyclohexanone, methyl isobutyl ketone, isobutylacetate and the like. These may be used alone or as mixed solventscomprising two or more different types.

The refractive index may be adjusted by adding superfine particles witha mean primary diameter of no greater than 100 nm to either or both thehigh refractive index layer and low refractive index layer. The meanprimary diameter is preferably no greater than 100 nm, and morepreferably no greater than 50 nm. By limiting the mean primary diameterof the superfine particles to no greater than 100 nm it is possible toform a satisfactory optical interference layer with no whitening of thecoated layer.

Examples of superfine particles having a mean primary diameter of nogreater than 100 nm include superfine particles of metal oxides such asAl₂O₃, Bi₂O₃, CeO₂, In₂O₃, In₂O₃.SnO₂, HfO₂, La₂O₃, Sb₂O₅, Sb₂O₅SnO₂,SnO₂, TiO₂, Y₂O₃, ZnO, ZrO₂ and the like, as well as superfine particlescomposed of metal fluorides such as MgF₂.

The transparent conductive laminate of the invention obtained in thismanner may be used as the movable electrode substrate or a fixedelectrode substrate of a touch panel.

The transparent conductive laminate of the invention described above maybe used for the electrode substrates of a touch panel, and the touchpanel may be used in a touch panel-equipped liquid crystal display.

The polarizing plate used in this case will be a polarizing film asdescribed below, laminated as necessary with a protective film on one orboth sides. As examples of polarizing films there may be mentioned (i)oriented iodine and/or dichromatic organic dye-based polarizing filmsobtained by adsorption of iodine and/or dichromatic organic dyes onhydrophilic polymer films such as polyvinyl alcohol-based films,partially formalated polyvinyl alcohol-based films, ethylene-vinylacetate copolymer-based saponified films and cellulose-based films, (ii)oriented polyene-based polarizing films obtained by dehydrationtreatment of polyvinyl alcohol-based films to form polyenes, and (iii)oriented polyene-based-polarizing films obtained by dehydrochlorinationof poly vinyl chloride films to form polyenes. These will ordinarily beused at thicknesses of 10-80 μm.

As polarizing films there may be used films produced by adding adichromatic organic dye in a hydrophobic polymer in advance and thencasting it into a film by a publicly-known process, stretching it in atleast one direction and heat setting it. The hydrophobic polymer may beany material which does not undergo changes such as shrinkage orexpansion under conditions with a temperature of 100° C. or below and arelative humidity of 80% or lower, and specific examples includepolyester-based resins such as polyethylene terephthalate andpolybutylene terephthalate, polycarbonate-based resins, polyamide-basedresins such as nylon-6, nylon-66 and nylon-12, polyvinyl chloride,polyolefin-based resins such as polypropylene, polyether-based resinsand polysulfone-based resins, among which polyethylene terephthalate,nylon-6, nylon-66 and nylon-12 are preferred. The dichromatic organicdye has dichroism based on its molecular structure, and it is mostpreferably heat resistant and weather resistant. Production of such apolarizing film is accomplished by mixing a dichromatic organic dye withthe hydrophobic polymer using a Henschel mixer, blender or the like andthen cast into a film by an ordinary publicly-known method such as T-dieextrusion, inflation, solution casting or the like, before being fed tothe stretching process. The stretching process is carried out toaccomplish stretching the film by as high power as possible in onedirection at a suitable temperature above the glass transition point andbelow the melting point of the resin, to increase the surface area whilereducing the thickness. In this case, the stretching direction is notparticularly restricted to one direction, and if necessary stretching bylow power may be carried out in the direction orthogonal to thedirection of stretching by high power in order to improve the mechanicalstrength of the film. Another type of polymer may also be blended withthe hydrophobic polymer in a range which does not inhibit the object ofthe invention, and there may be added various inorganic or organicadditives such as antioxidants, heat stabilizers, lubricants,ultraviolet absorbers, nucleating agents or surface protrusion-formingagents. The thicknesses of such polarizing films are preferably 20-200μm.

As mentioned above, a protective film may be laminated on one or bothsides of the polarizing film if necessary. As the protective film theremay be used an optical isotropy film with a retardation value of nogreater than 30 nm, and/or a film stretched only in one direction.Particularly when a polarizing plate is used on the input operationside, a protective film is preferably laminated on the side of thepolarizing film opposite to the side on which the transparent conductivelaminate is to be laminated, for increased reliability.

As optical isotropy films having retardation values of no greater than30 nm, to be used as the aforementioned protective film, there may bementioned films made of polycarbonate-based resins, polysulfone-basedresins such as polysulfone, polyethersulfone and polyallylsulfone,polyolefin-based resins, acetate-based resins such as cellulosetriacetate and polyallylate-based resins, having thicknesses of 10-20μm.

As plastic films stretched in only one direction for use as theprotective film there may be mentioned films obtained by stretchingresins, for example, polyester-based resins such as polyethyleneterephthalate, polyethylene isophthalate, polyphenylene isophthalate,polybutylene terephthalate and polyethylene-2,6-naphthalate,polysulfone-based resins such as polysulfone, polyethersulfone andpolyallylsulfone, polymethylpentene, polystyrene, polyolefin, polyamide,polymethyl methacrylate, polyvinyl chloride and triacetate, in a singledirection, but from the standpoint of chemical resistance, theaforementioned polyester films stretched to at least 5% and preferably50-80% in only the longitudinal or lateral direction, and heat set from100° C.×60 min to 230° C.×5 min to a thickness of 10-200 μm, arepreferred.

Also, when the polarizing plate is used on the input operation side ofthe touch panel, a layer having an anti-reflection function, ananti-glare function or an abrasion resistant function may be formed onthe input operation side of the polarizing plate.

The transparent conductive laminate (R) of the invention is a laminatehaving a transparent conductive layer on at least one surface of atransparent substrate made of a polymer film or glass. As a polymer filmthere may be used the same type as the polymer film A, made of a polymerhaving a photoelastic constant of no greater than 70×10⁻¹² Pa⁻¹(70×10⁻¹³ cm²/dyne), which is used in the transparent conductivelaminate (P) of the invention. Such a polymer film may consist of two ormore laminated layers, or it may be laminated with a glass substrate.However, the retardation value of the transparent substrate must conformto the optical design of the overall touch panel-equipped liquid crystaldisplay.

The thickness of the transparent substrate is preferably 50-2000 μm, andmore preferably 75-1500 μm. With a thickness of less than 50 μm,manufacturing the transparent conductive layer is rendered moredifficult. If the thickness is greater than 2000 μm, the thickness ofthe touch panel becomes too large, making it unsuitable for use inportable information-processing equipments.

The transparent substrate is preferably either an optical isotropysubstrate with a retardation value of no greater than 30 nm, or asubstrate exhibiting a ¼ wavelength retardation.

When the transparent substrate is an optical isotropy substrate, thetouch panel is preferably fabricated with the optical axis of thetransparent conductive laminate R aligned either parallel or orthogonalto the optical axis of the transparent conductive laminate P.

When the transparent substrate is a substrate exhibiting a ¼ wavelengthretardation, the transparent conductive laminate R may also serve as theretardation film 2. In this case, the touch panel is fabricated so thatthe optical axis of the transparent conductive laminate R and theoptical axis of the transparent conductive laminate P may be alignedorthogonal to each other.

The touch panel of the invention may be usually used with a ReflectiveLCD, Transmissive LCD or Transflective LCD, which require polarizingplates for producing an image. As examples there may be mentionedvarious modes of liquid crystal displays such as TN, STN, ECB(Electrically Controlled Birefringence), CSH (Color Super Homeotropic),OCB (Optical Compensated Bend), HAN (Half Aligned Nematic), VA (VerticalAligned), IPS (In-Plane Switching), ferroelectric, antiferroelectric,cholesteric phase transition and GH (Guest Host).

The touch panel of the invention exhibits a significant effect when usedin combination with a liquid crystal display, but it may also be usedfor displays other than a liquid crystal display. An OLED (OrganicLight-Emitting Diode) may be mentioned, for example.

A touch panel fabricated in the manner described above may be mounted ona display such as a liquid crystal display (LCD), OLED (OrganicLight-Emitting Diode) or the like, specifically on the viewing side, toproduce a circular polarizing plate-type “inner” touch panel-equippeddisplay, or an integrated-type “inner” touch panel-equipped display.

EFFECT OF THE INVENTION

According to the invention there is provided a transparent conductivelaminate which can be used to produce a touch panel with excellentvisibility and no coloration at high temperatures, as well as touchpanel-equipped liquid crystal displays employing it.

EXAMPLES

The invention will now be explained in greater detail through thefollowing examples, with the understanding that the invention is in noway limited by the examples.

(Evaluation Methods)

(1) Measurement of Retardation Value and Photoelastic Constant

The retardation value and photoelastic constant were measured using an“M150” spectroscopic ellipsometer (JASCO Corp.)

(2) Measurement of Glass Transition Temperature (Tg) of Polymer

This was measured using a “DSC2920 Modulated DSC” (TA Instruments). Themeasurement was performed after polymerization of the resin, in the formof flakes or chips, before casting the film.

(3) High Temperature Test of Touch Panel

The touch panel was placed on a 80° C.-heated mirror surface hot platewith the polarizing plate facing upward, and the color change of thetouch panel was examined after leaving for one minute.

(4) Observation of Color Stripes in Touch Panel

The color stripes were observed from the polarizing plate side of thetouch panel under a three wavelength fluorescent lamp.

The monomer structures of the polycarbonate used in the examples andcomparative examples are shown below.

Example 1 and Comparative Example

Aqueous sodium hydroxide and ion-exchanged water were charged into areactor equipped with a stirrer, thermometer and reflux condenser,monomers (E) and (F) having the structures shown above were dissolved ina molar ratio of 50:50, and a small amount of hydrosulfite was added.After adding methylene chloride, phosgene was blown in at 20° C. forapproximately 60 minutes. Next, p-tert-butylphenol was added foremulsification, triethylamine was added, and the mixture was stirred at30° C. for approximately 3 hours to complete the reaction. Uponcompletion of the reaction, the organic phase was separated, and themethylene chloride was evaporated off to obtain a polycarbonatecopolymer. The compositional ratio of the obtained copolymer wasapproximately equivalent to the monomer charging ratio. The glasstransition temperature was 215° C.

The copolymer was then dissolved in methylene chloride to prepare a dopesolution with a solid concentration of 18 wt %. A film was cast from thedope solution, and the film was uniaxially stretched at 220° C. by1.30-power in the longitudinal direction to obtain a retardation film(3) having a thickness of 95 μm, a retardation value of 138 nm and aphotoelastic constant of 60×10⁻¹² Pa⁻¹.

Next, coating solution A was prepared comprising 50 parts by weight of apolyester acrylate (ARONIX M8060, product of TOAGOSEI Co., Ltd.), 50parts by weight of dipentaerythritol hexaacrylate (DPHA, product ofNippon Kayaku Co., Ltd.), 7 parts by weight of a photoinitiator(IRGACURE 184, product of Ciba-Geigy) and 200 parts by weight of1-methoxy-2-propanol as a diluent. To the coating solution A there werethen added silicone crosslinked fine particles with a mean diameter ofabout 3 μm (TOSPEARL 130, product of GE Toshiba Silicones) as fineparticles, at 0.2 part by weight to 100 parts by weight of the resincomponent, to obtain coating solution B. Separately, the siliconecrosslinked fine particles with a mean diameter of about 3 μm (TOSPEARL130, product of GE Toshiba Silicones) were added as fine particles tothe coating solution A at 0.5 part by weight to 100 parts by weight ofthe resin component, to obtain coating solution C.

Coating solution B was coated onto one side of the retardation film (3)using a microgravure coater and dried at 60° C. for 1 minute, and then ahigh-pressure mercury lamp was used at an intensity of 160 w/cm forcuring of the coated layer under a cumulative dose of 450 mJ/cm² to forma light-scattering layer (2) with a thickness of approximately 2 μm. Thehaze value of the light-scattering layer alone was 0.5%. A microgravurecoater was then used to coat coating solution C onto the side of theretardation film (3) opposite to the side on which the light-scatteringlayer was formed, and then after drying at 60° C. for 1 minute, ahigh-pressure mercury lamp was used at an intensity of 160 w/cm forcuring of the coated layer under a cumulative dose of 450 mJ/cm² to forma cured resin layer (4) with a thickness of approximately 2 μm.

Next, an indium-tin oxide target with indium oxide and tin oxide in aweight ratio of 9:1 and a packing density of 98% was used for forming anITO layer on the cured resin layer (4) by sputtering, to obtain atransparent conductive laminate (14-1) for Example 1. The thickness ofthe ITO layer was 20 nm, and the resistance value was 330Ω/□. Theretardation value was virtually unchanged at 137 nm.

Coating solution A was coated onto one side of the retardation film (3)using a microgravure coater and dried at 60° C. for 1 minute, and then ahigh-pressure mercury lamp was used at an intensity of 160 w/cm forcuring of the coated layer under a cumulative dose of 450 mJ/cm² to forma transparent resin layer with a thickness of approximately 2 μm. Thehaze value of the transparent resin layer alone was 0%. In a similarmanner, coating solution C was used to form a cured resin layer with athickness of approximately 2 μm on the side of the retardation film (3)opposite to the side on which the transparent resin layer was formed. AnITO layer was similarly formed on the cured resin layer to obtain atransparent conductive laminate (14-1) for Comparative Example 1. Thethickness of the ITO layer was 20 nm and the resistance value was340Ω/□. The retardation value was virtually unchanged at 137 nm.

Separately, an SiO₂ layer was formed on both sides of a 1.1 mm-thickglass substrate (8) by dip coating, and then an 18 nm-thick ITO layerwas formed by sputtering as a transparent conductive layer to obtain atransparent conductive laminate (15). Dot spacers with a 7 μm height, 70μm diameter and 1.5 mm pitch were then formed on the ITO layer.

Next, after forming an external lead circuit, insulating layer andadhesive layer, the transparent conductive laminate (14-1) andtransparent conductive laminate (15) were attached together so that thetransparent conductive layer (ITO layer) sides of the transparentconductive laminate (14-1) and transparent conductive laminate (15)might face each other, to fabricate an analog-type touch panel.

A triacetate film was laminated onto both sides of a uniaxiallystretched polyvinyl alcohol film comprising iodine as a polarizer via anadhesive to obtain a 150 μm-thick polarizing plate (13) for the inputoperation side. An anti-glare hard coat layer was formed on the inputoperation side of the polarizing plate (13).

The polarizing plate (13) and the transparent conductive laminate (14-1)were laminated via an adhesive so that the optical axis of thepolarizing plate (13) and the optical axis of the retardation film (3)might forman angle of 45°, to fabricate touch panels for Example 1 andComparative Example 1.

The touch panels were subjected to high-temperature testing and colorstripes observation. The results are shown in Table 1.

Example 2

An approximately 2 μm-thick light-scattering layer (2) was formed on oneside of the retardation film (3) of Example 1 in the same manner asExample 1. The haze value of the light-scattering layer alone was 0.5%.An approximately 2 μm-thick cured resin layer (4) was then formed on theside of the retardation film (3) opposite to the side on which thelight-scattering layer was formed, in the same manner as Example 1.

Next, tetrabutoxy titanate (“B-4” by Nihon Soda) was diluted with amixed solvent of ligroin (special grade product by Wako Pure ChemicalIndustries) and butanol (special grade product by Wako Pure ChemicalIndustries) to prepare coating solution D.

γ-Glycidoxypropyltrimethoxysilane (“KBM403” by Shin-Etsu Chemical Co.,Ltd.) and methyltrimethoxysilane (“KBM13” by Shin-Etsu Chemical Co.,Ltd.) were mixed in a molar ratio of 1:1 and hydrolysis of the silaneswas carried out by a publicly-known method with aqueous acetic acid(pH=3.0) to obtain silane hydrolysate. Next,N-β(aminoethyl)-γ-aminopropylmethoxysilane (“KBM603” by Shin-EtsuChemical Co., Ltd.) was added at 1 part by weight to 20 parts by weightof the aforementioned silane hydrolysate, and the mixture was dilutedwith a mixed solution of isopropyl alcohol and n-butanol to preparealkoxysilane coating solution E.

After mixing coating solution D and coating solution E so that thetetrabutoxy titanate component of coating solution D and thealkoxysilane component of coating solution E might be in a weight ratioof 70:30, TiO₂ superfine particles having a primary diameter of 20 nmwere mixed with the solution mixture so that the TiO₂ superfineparticles and the metal alkoxide (total of tetrabutoxy titanate andalkoxysilane) might be in a weight ratio of 30:70, to prepare coatingsolution F. Coating solution F was coated onto the cured resin layer ofthe retardation film 3 using a microgravure coater and then dried at130° C. for 2 minutes to form a high refractive index layer (9) with athickness of 55 nm. Next, coating solution E was coated onto the highrefractive index layer using a microgravure coater and dried at 130° C.for 2 minutes to form a low refractive index layer (10) with a thicknessof 45 nm, thereby forming an optical interference layer comprising ahigh refractive index layer and a low refractive index layer. Anindium-tin oxide target with indium oxide and tin oxide in a weightratio of 9:1 and a packing density of 98% was used to form an ITO layeron the low refractive index layer by sputtering, to obtain a transparentconductive laminate (14-2) for Example 2. The ITO layer thickness wasapproximately 20 nm, and the surface resistance was approximately300Ω/□. The retardation value was virtually unchanged at 137 nm.

Separately, dot spacers with a 7 μm height, 70 μm diameter and 1.5 mmpitch were formed on the ITO layer of the transparent conductivelaminate (15) by exactly the same method as Example 1.

Next, after forming an external lead circuit, insulating layer andadhesive layer, the transparent conductive laminate (14-2) andtransparent conductive laminate (15) were attached together so that thetransparent conductive layer sides of the transparent conductivelaminate (14-2) and transparent conductive laminate (15) might face eachother, to fabricate an analog-type touch panel.

A polarizing plate (13) was obtained in exactly the same manner asExample 1. An anti-glare hard coat layer was formed on the inputoperation side of the polarizing plate (13).

The polarizing plate (13) and the transparent conductive laminate (14-2)were laminated via an adhesive so that the optical axis of thepolarizing plate (13) and the optical axis of the retardation film (3)might forman angle of 45°, to fabricate a touch panel for Example 2.

The touch panel was subjected to high-temperature testing and colorstripes observation. The results are shown in Table 1.

High temperature Color stripes testing results observation resultsExample 1 No coloration No interference color stripes Example 2 Nocoloration No interference color stripes Comparative No colorationInterference color stripes were seen Example 1

Example 3 and Comparative Example 2

A λ/4 retardation film (18) was attached to the polarizing plate (19) ofa liquid crystal display comprising a polarizing plate (19), retardationfilm (20), liquid crystal cell (21) and polarizing plate (22), in such amanner that the optical axis of the polarizing plate (19) and theoptical axis of the retardation film (18) formed an angle of 135°. Next,the touch panel of Example 2 was situated on the liquid crystal displayacross a gap of 0.4 mm so that the optical axis of the polarizing plate(13) and the optical axis of the polarizing plate (19) might beparallel, to fabricate a circular polarizing plate-type touchpanel-equipped liquid crystal display. The liquid crystal displayproduced clearly visible images even outdoors. No color change was seenin the liquid crystal display with or without the touch panel.

A transparent conductive laminate (Comparative Example 2) was alsoobtained using the following retardation film instead of the retardationfilm (3) of the transparent conductive laminate of the touch panel ofExample 2. Specifically, C1400 (glass transition temperature: 155° C.)by Teijin Chemicals Ltd. was dissolved in methylene chloride to preparea dope solution with a solid concentration of 18 wt %. A film was castfrom the dope solution and uniaxially stretched by 1.05-power in thelongitudinal direction at 155° C. to obtain a retardation film (3) witha thickness of 70 μm, a retardation value of 138 nm and a photoelasticconstant of 90×10⁻¹² Pa⁻¹.

Next, a light-scattering layer was formed on one side of the retardationfilm (3) in exactly the same manner as Example 2. A cured resin layer, ahigh refractive index layer, a low refractive index layer and an ITOlayer were formed in that order on the side opposite to the side onwhich the light-scattering layer was formed to obtain a transparentconductive laminate (14-2). The thickness of the ITO layer was 20 nm,and the resistance value was 310Ω/□. The retardation value changed to148 nm.

The transparent conductive laminate (14-2) was used to fabricate a touchpanel-equipped liquid crystal display having the same construction asExample 3. Outdoors, the liquid crystal display had a more yellow tintas compared to absence of the touch panel. High temperature testing ofthe touch panel produced arc-shaped coloration from the adhesive (seal)section toward the interior.

Example 4

Coating solution G was prepared comprising 100 parts by weight ofurethane acrylate, 7 parts by weight of a photoinitiator (IRGACURE 184,product of Ciba-Geigy), 135 parts by weight of 1-methoxy-2-propanol as adiluent and 135 parts by weight of isopropanol. To the coating solutionG there were then added silicone crosslinked fine particles with a meandiameter of about 3 μm (TOSPEARL 130, product of GE-Toshiba Silicones)as fine particles A, at 0.2 part by weight to 100 parts by weight of theresin component, to obtain coating solution H. Separately, there wereadded to the coating solution G the silicone crosslinked fine particleswith a mean particle size of about 3 μm (TOSPEARL 130, product ofGE-Toshiba Silicones) as fine particles A at 0.7 part by weight to 100parts by weight of the resin component, and MgF₂ superfine particles assuperfine particles B at 5 parts by weight to 100 parts by weight of theresin component, to obtain coating solution I.

Coating solution H was coated onto one side of a polymer film (12)(ZEONOR film, ZF14-100, product of Nihon Zeon) having a thickness of 100μm, a glass transition temperature of 136° C., a retardation value of5.5 nm and a photoelastic constant of 6.5×10⁻¹² Pa⁻¹ using amicrogravure coater and dried at 60° C. for 1 minute, and then ahigh-pressure mercury lamp was used at an intensity of 160 w/cm forcuring of the coated layer under a cumulative dose of 450 mJ/cm² to forma light-scattering layer (2) with a thickness of approximately 2 μm. Thehaze value of the light-scattering layer alone was 0.5%. A microgravurecoater was then used to coat coating solution I onto the side of thepolymer film (12) opposite to the side on which the light-scatteringlayer was formed, and then after drying at 60° C. for 1 minute, ahigh-pressure mercury lamp was used at an intensity of 160 w/cm forcuring of the coated layer under a cumulative dose of 450 mJ/cm² to forma cured resin layer (4) with a thickness of approximately 2 μm.

Next, coating solution E and coating solution F were prepared in thesame manner as Example 2. Coating solution F was coated onto the curedresin layer (4) of the polymer film (12) using a microgravure coater andthen dried at 125° C. for 2 minutes to form a high refractive indexlayer (9) with a thickness of 55 nm. Coating solution E was then coatedonto the high refractive index layer using a microgravure coater andthen dried at 125° C. for 2 minutes to form a low refractive index layer(10) with a thickness of 45 nm, thereby forming an optical interferencelayer comprising a high refractive index layer and a low refractiveindex layer. An indium-tin oxide target with indium oxide and tin oxidein a weight ratio of 9:1 and a packing density of 98% was used to forman ITO layer on the low refractive index layer by sputtering, therebyobtaining a transparent conductive laminate (16). The ITO layerthickness was approximately 20 nm, and the surface resistance wasapproximately 300Ω/□. The retardation value was virtually unchanged. Asingle layer λ/4 retardation film (11) and a single layer λ/2retardation film (3) was laminated to the light-scattering layer (2) ofthe transparent conductive laminate to obtain a transparent conductivelaminate (17).

Separately, Dot spacers with a 7 μm height, 70 μm diameter and 1.5 mmpitch were formed on the ITO layer of the transparent conductivelaminate (16) by exactly the same method as Example 1.

Next, after forming an external lead circuit, insulating layer andadhesive layer the transparent conductive laminate (17) and transparentconductive laminate (16) were attached together so that the transparentconductive layer sides of the transparent conductive laminate (16) andtransparent conductive laminate (17) might face each other, to fabricatean analog-type touch panel.

A polarizing plate (13) was obtained in exactly the same manner asExample 1. An anti-glare hard coat layer was formed on the inputoperation side of the polarizing plate (13).

The polarizing plate (13) was laminated to the transparent conductivelaminate (17) via an adhesive to obtain a touch panel. The touch panel,a liquid crystal cell (21) and a polarizing plate (22) were thenlaminated to fabricate an integrated-type touch panel-equipped liquidcrystal display for Example 4. The liquid crystal display producedclearly visible images even outdoors.

INDUSTRIAL APPLICABILITY

The transparent conductive laminate of the invention has reduced lightreflection with no coloration, and also has satisfactory productivity.The laminate may therefore be used to provide touch panels withexcellent visibility and high reliability for outdoor use, as well astouch panel-equipped liquid crystal displays employing them.

1. A transparent conductive laminate comprising: a film made of apolymer with a photoelastic constant of no greater than 70×10⁻¹² Pa⁻¹(polymer film A), a light-scattering layer with a haze value in therange of 0.2-1.4% formed directly on one side thereof, and a transparentconductive layer formed on the other side thereof, wherein the laminateexhibits a λ/4 retardation, wherein an optical interference layercomprising a high refractive index layer and a low refractive indexlayer is formed between said polymer film A and said transparentconductive layer so that said transparent conductive layer is in contactwith the low refractive index layer side, the high refractive indexlayer and low refractive index layer are both made of crosslinkedpolymers wherein a cured resin layer is between said first polymer filmand said transparent conductive layer, and wherein said cured resinlayer contains first fine particles having a mean primary diameter of0.5-5 μm and second fine particles having a mean primary diameter of nogreater than 100 nm, and wherein said cured resin has a first fineparticle content of at least 0.3 part by weight and less than 1.0 partby weight to 100 parts by weight of a cured resin component.
 2. Atransparent conductive laminate comprising: a film made of a polymerwith a photoelastic constant of no greater than 70×10-12 Pa⁻¹ (polymerfilm A), a light-scattering layer with a haze value in the range of0.2-1.4% formed on one side of polymer film A, and a transparentconductive layer formed on the other side of polymer film A, and a curedresin layer formed between said polymer film A and said transparentconductive layer, said cured resin layer containing two types of fineparticles, wherein said two types of particles includes first particleshaving a mean primary diameter of 0.5-5 μm and second particles having amean primary diameter of no greater than 100 nm, and wherein thelaminate exhibits a λ/4 retardation.
 3. The transparent conductivelaminate according to claim 2, wherein a center line average roughness(Ra) of said light scattering layer is 0.005-0.04 μm.
 4. The transparentconductive laminate according to claim 2, wherein said polymer film A isa thermoplastic resin with a glass transition temperature (Tg) of 170°C. or above.
 5. A transparent conductive laminate according to claim 4,wherein said thermoplastic resin is a polycarbonate.
 6. A transparentconductive laminate according to claim 2, wherein said polymer film A isa single layer λ/4 retardation film.
 7. A transparent conductivelaminate according to claim 2, wherein said polymer film A is a laminatefilm having two or more layers, said two or more layers including asingle layer λ/4 retardation film and a single layer λ/2 retardationfilm.
 8. A transparent conductive laminate according to claim 2, whereinsaid polymer film A is between a third polymer film and said transparentconductive layer, said third polymer film having a photoelastic constantof no greater than 70×10⁻¹² Pa⁻¹.
 9. A transparent conductive laminateaccording to claim 8, wherein said polymer film A has a retardationvalue of no greater than 30 nm, and said third polymer film is alaminated retardation film comprising a single layer λ/4 retardationfilm and a single layer λ/2 retardation film.
 10. A transparentconductive laminate according to claim 9, wherein said polymer film A isa single layer λ/4 retardation film, and said third polymer film is asingle layer λ/2 retardation film.
 11. A transparent conductive laminateaccording to claim 2, wherein an optical interference layer is betweensaid polymer film A and said transparent conductive layer.
 12. Atransparent conductive laminate according to claim 11, wherein a curedresin layer is between said polymer film A and said optical interferencelayer.
 13. A transparent conductive laminate according to claim 11,wherein said optical interference layer comprises a high refractiveindex layer and a low refractive index layer, said high and lowrefractive index layers being crosslinked polymers.
 14. A transparentconductive laminate according to claim 13, wherein said transparentconductive layer is in contact with said low refractive index layer. 15.A touch panel comprising: the transparent conductive laminate accordingto claim 2, wherein a first polarizing plate is formed on a side of saidlight-scattering layer, and wherein a gap is between said movableelectrode substrate and said fixed electrode substrate.
 16. A touchpanel-equipped liquid crystal display comprising: the touch panelaccording to claim 15; a liquid crystal cell between said touch paneland a second polarizing plate.
 17. The touch panel-equipped liquidcrystal display according to claim 16, wherein a third polarizing plateis between two retardation films, said liquid crystal cell being betweensaid third polarizing plate and said second polarizing plate.